SACRAMENTO  Californians could soon invest in trees to offset the greenhouse gases they pump into the air when they heat their homes or drive to work.

The nonprofit California Climate Action Registry was set up by the state six years ago to encourage corporations and government agencies to track, and ultimately reduce, their emissions. The Forest Protocols program will allow environmentally minded citizens to pay to preserve enough trees to offset their personal carbon emissions.

The registry has calculated how much the timber industry loses by allowing trees to grow longer and bigger -- past the time they are normally harvested. The industry would then be compensated by other companies that buy carbon credits -- or shares of the trees -- to offset their carbon emissions.

Scientists blame emissions of carbon dioxide and other gases for helping cause global warming, which researchers predict will lead to stronger storms, more severe droughts and bigger wildfires.

The Pacific Forest Trust manages the five parcels of timberland owned by the Fred M. van Eck Forest Foundation, and they jointly registered the 2,100-acre (840-hectare) property with the state. Negotiations are under way to set the prices for its carbon credits.

For instance, Pacific Gas and Electric Co. in January asked the California Public Utilities Commission to let it start a program next year where customers could choose to pay about 3 percent more on each monthly bill, with the money earmarked to preserve trees in a registered forest.

The utility pumps about 5.3 tons (4.8 metric tons) of carbon dioxide into the atmosphere each year to supply the electricity and natural gas used by a typical household. If the homeowner opted to pay about $4.31 (euro3.40) each month to be invested in forests, the trees would store an equivalent amount of carbon.

"It would cost them about $4.31 a month to become climate neutral," said Wendy Pulling, PG&E's director of environmental policy.

PG&E is the first utility in the U.S. seeking such a program for its five million electric and 4.2 million natural gas customers, Pulling said. The company serves about 14 million people in northern and central California.